Article: A First-principles Model Of Early Evolution

A First-principles Model Of Early Evolution

Science Daily - In a study publishing in PLoS Computational Biology,
Shakhnovich et al present a new model of early biological evolution -- the
first that directly relates the fitness of a population of evolving model
organisms to the properties of their proteins.

Key to understanding biological evolution is an important, but elusive,
connection, known as the genotype-phenotype relationship, which translates
the survival of entire organisms into microscopic selection for particular
advantageous genes, or protein sequences. The study of Shakhnovich et al
establishes such connections by postulating that the death rate of an
organism is determined by the stability of the least stable of their
proteins.

The simulation of the model proceeds via random mutations, gene duplication,
organism births via replication, and organism deaths.

The authors find that survival of the population is possible only after a
''Big Bang'' when a very small number of advantageous protein structures is
suddenly discovered and exponential growth of the population ensues. The
subsequent evolution of the Protein Universe occurs as an expansion of this
small set of proteins through a duplication and divergence process that
accompanies discovery of new proteins.

The model resolves one of the key mysteries of molecular evolution -- the
origin of highly uneven distribution of fold family and gene family sizes in
the Protein Universe. It quantitatively reproduces these distributions
pointing out their origin in biased post "Big Bang'' evolutionary dynamics
of discovery of new proteins. The number of genes in the evolving organisms
depends on the mutation rate, demonstrating the intricate relationship
between macroscopic properties of organisms -- their genome sizes -- and
microscopic properties -- stabilities -- of their proteins.

The results of the study suggest a plausible comprehensive scenario of
emergence and growth of the Protein Universe in early biological evolution.
Article: Zeldovich KB, Chen P, Shakhnovich BE, Shakhnovich EI (2007) A
first-principles model of early evolution: Emergence of gene families,
species, and preferred protein folds. PLoS Comput Biol 3(7): e139.
doi:10.1371/journal.pcbi.0030139

Source: Public Library of Science
http://www.sciencedaily.com/releases/2007/07/070711105750.htm

Posted by
Robert Karl Stonjek


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